The central data bank of the Rochester Program Project (RPP) consists of a file of medical diagnoses and surgical procedures covering the population of Rochester and Olmsted County, MN. for a period of more than 40 years. These data have been assembled from records at Mayo Clinic and other medical care centers and are considered a national resource for epidemiological studies. The medical records upon which this resource depends cover essentially all local physician-patient contacts and include records for home, outpatient and hospital visits, and autopsy data. This resource is maintained at the Mayo Clinic but is available to visiting scientists, students from other universities, and health agencies. More than 100 epidemiological studies using this data bank have been completed. These include studies of incidence and outcome as well as case-control comparisons and prospective studies. Studies underway at the present time include several on diabetes and breast cancer and descriptive studies on epilepsy and head trauma, Guillain-Barre syndrome, leukemia, rheumatoid arthritis and carpal tunnal syndrome. A new study of urolithiasis incidence and recurrence rates over the past 25 years will also be reported soon. A new and natural extension of the RPP is the Birth Cohort Family File (BCFF) which will include information pertaining to 25,000 births, their parents and siblings for a total of approximately 75,000 persons. In addition to medical diagnoses, the BCFF will contain information on specific laboratory tests, diagnostic and therapeutic procedures and drugs prescribed during pregnancy. The addition of diagnostic information concerning those conditions which are less than life threatening will enhance the present diagnostic index. A family linkage system has been designed that will enable study of familial associations of many conditions. A series of new etiologic studies are planned including urinary tract infection in children, atopic disease, mental retardation, and congenital malformation.